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United States Patent |
6,262,152
|
Fryd
,   et al.
|
July 17, 2001
|
Particles dispersed w/polymer dispersant having liquid soluble and
cross-linkable insoluble segments
Abstract
Dispersions containing a liquid vehicle (which can be aqueous, semi-aqueous
or non-aqueous), organic or inorganic particles (or mixtures) that are
insoluble in the liquid vehicle and a polymeric dispersant, preferably a
structured polymeric dispersant, having one or more segments soluble in
the liquid vehicle and one or more segments insoluble in the liquid
vehicle, have improved stability when the insoluble segment(s) contains
cross-linking groups which are cross-linked to itself or a cross-linking
compound such as a polyfunctional monomer, oligomer or polymer to form an
encapsulation network that entraps the particles which are particularly
useful for paints or inks in coating and printing applications.
Inventors:
|
Fryd; Michael (Moorestown, NJ);
Visscher; Karyn B. (Voorhees, NJ)
|
Assignee:
|
E. I. du Pont de Nemours and Company (Wilmington, DE)
|
Appl. No.:
|
342808 |
Filed:
|
June 29, 1999 |
Current U.S. Class: |
524/90; 523/205; 524/210; 524/388; 524/389; 524/391; 524/413; 524/430; 524/440; 524/441; 524/548; 524/558; 525/123 |
Intern'l Class: |
C08K 003/08; C08K 003/20; C08K 003/22; C08K 005/07; C08L 051/00 |
Field of Search: |
523/205
524/533,90,210,388,389,391,413,430,440,441,548,558
525/123
|
References Cited
U.S. Patent Documents
3393162 | Jul., 1968 | Cox et al. | 523/205.
|
3640863 | Feb., 1972 | Okuno et al. | 523/205.
|
3912677 | Oct., 1975 | Baker et al. | 523/205.
|
4251287 | Feb., 1981 | Lim et al. | 252/316.
|
4337185 | Jun., 1982 | Wessling et al. | 524/458.
|
4405744 | Sep., 1983 | Greinecker et al. | 523/205.
|
4418163 | Nov., 1983 | Murakami et al. | 523/205.
|
4597794 | Jul., 1986 | Ohta et al. | 523/160.
|
4698215 | Oct., 1987 | Albanesi et al. | 523/205.
|
4798691 | Jan., 1989 | Kasai et al. | 264/47.
|
4798786 | Jan., 1989 | Tice et al. | 435/177.
|
4931284 | Jun., 1990 | Ekman et al. | 424/450.
|
4935456 | Jun., 1990 | Huang et al. | 523/201.
|
4985166 | Jan., 1991 | Leising et al. | 252/62.
|
5162189 | Nov., 1992 | Pierce et al. | 430/126.
|
5225278 | Jul., 1993 | Kielbania, Jr. et al. | 428/402.
|
5417890 | May., 1995 | Epron et al. | 252/500.
|
5521253 | May., 1996 | Lee et al. | 525/301.
|
5618888 | Apr., 1997 | Choi et al. | 525/301.
|
5629401 | May., 1997 | Graiver et al. | 528/43.
|
6051060 | Apr., 2000 | Mizobuchi | 523/205.
|
6057384 | May., 2000 | Nguyen et al. | 523/160.
|
6080802 | Jun., 2000 | Emmons et al. | 523/205.
|
6096802 | Aug., 2000 | Lark | 523/205.
|
6117921 | Sep., 2000 | Ma et al. | 524/533.
|
Foreign Patent Documents |
0 340 976 A2 | Nov., 1989 | EP.
| |
0 540 757 A1 | May., 1993 | EP.
| |
0 722 994 A1 | Jul., 1996 | EP.
| |
0 775 596 | May., 1997 | EP.
| |
1035445 | Jun., 1966 | GB.
| |
55-139471 | Oct., 1980 | JP.
| |
Primary Examiner: Sellers; Robert E. L.
Attorney, Agent or Firm: Tessari; Joseph A.
Parent Case Text
This application claim benefit to U.S. provisional 60/103194 filed Oct. 6,
1998.
Claims
What is claimed is:
1. A dispersion of particles in a liquid vehicle, comprising:
(a) a liquid vehicle selected from the group consisting of water, organic
solvents and combinations thereof, wherein the vehicle comprises at least
50% by weight of water;
(b) particles that are at least substantially insoluble in the liquid
vehicle;
(c) a polymer dispersant having at least one segment soluble in the liquid
vehicle and at least one segment insoluble in the liquid vehicle, said
insoluble segment having cross-linkable moieties; and
(d) wherein the cross-linkable moieties on the insoluble segment of the
polymer dispersant are cross-linked such that the insoluble segment of the
polymer dispersant forms a cross-linked polymer matrix with the particles
entrapped therein.
2. The dispersion of claim 1, wherein the particle comprises a pigment.
3. The dispersion of claim 1, wherein the cross-linkable moieties on the at
least one insoluble segment of the polymer comprise hydroxyl groups and
wherein the dispersion further comprises a diisocyante as a cross-linkable
component.
4. The dispersion of claim 1, further comprising a cross-linkable component
having a cross-linking moiety selected from the group consisting of amine,
anhydride, acid, phenolic, hydroxyl, N-methylol, aldehyde, acetoacetoxy,
isocyanate, epoxide, ester, isocyanate, aldehyde, activated allyl and
water.
5. The dispersion of claim 1, wherein the cross-linkable moieties on the at
least one insoluble segment of the polymeric dispersant are selected from
the group consisting of epoxy, hydroxyl, anhydride, acid, cyclic
carbonate, activated allyl, amine, silane, silicate, silanol, silicone and
imine.
6. The dispersion of claim 1, further comprising a catalyst to facilitate
cross-linking.
7. The dispersion of claim 6, wherein said catalyst is selected from the
group consisting of 2,2,2-diaminobicyclooctane, dibutyltin dilaurate,
tributyl amine, trioctyl amine, tridodecyl amine and dimethyldodecyl
amine.
8. A dispersion of particles in a liquid vehicle, comprising:
a) a liquid vehicle selected from the group consisting of water, organic
solvents and combinations thereof;
b) particles that are at least substantially insoluble in the liquid
vehicle;
c) a polymer dispersant having at least one segment soluble in the liquid
vehicle and at least one segment insoluble in the liquid vehicle, said
insoluble segment having cross-linkable moieties;
d) wherein the cross-linkable moieties on the insoluble segment of the
polymer dispersant are cross-linked such that the insoluble segment of the
polymer dispersant forms a cross-linked polymer matrix with the particles
entrapped therein; and
e) wherein the cross-linkable moieties comprise hydroxyl groups and wherein
the dispersion further comprises a diisocyanate as a cross-linkable
component.
Description
BACKGROUND OF THE INVENTION
This invention relates to dispersions of particles in a liquid vehicle and,
more particularly, to dispersions in which the particles are entangled in
a cross-linked polymer matrix.
Dispersions of particles in a liquid vehicle are commonly used in a wide
variety of industries and processes, such as coatings (e.g., paint and
ink), magnetic or optical recording media (e.g., tapes and disks),
cosmetics (e.g., lipsticks and nail polish); agriculture (e.g.,
insecticides), pharmaceutical preparations and many others. In addition,
in a concentrated form (such as can be obtained by centrifugation followed
by decanting the supernatant liquid) the dispersions are useful for
tinting, coloring fibers, coloring molded resins, for adding pigment to
flexographic plates and a variety of other applications.
As expected, these dispersions are very diverse. Generally speaking,
however, these dispersions all contain a liquid vehicle (such as water, an
organic solvent, or a combination of the two) and some type of particle
(such as a pigment, a pharmaceutically active compound, metallic flakes,
hollow glass spheres, discrete polymer particles, etc.). Typically, but
not always, a dispersant is used to help maintain the particles in a
suspended state in the liquid vehicle; i.e., prevent the particles from
settling out of the liquid. In many instances, the dispersant used is a
polymer.
There has been significant effort in the art directed at improving the
stability of the dispersions so that the particles are less likely to
settle out of the liquid under a defined set of conditions. The reason for
the effort is that a dispersion with improved stability can translate into
products having a longer shelf life; products that can survive more
rigorous storage conditions (e.g., extreme temperature cycles); products
that are easier or less expensive to transport or handle during use; and
products that are more uniform and consistent in quality, and products
that offer greater formulation latitude.
The effort to improve dispersion stability to date have included
improvements in the processes used to make the dispersions, the
development of new dispersants and the exploration of the interaction
between dispersants and particular liquid vehicle formulations. Recently,
there has been a good deal of research directed at modifying the
particles, especially the particle surface, in order to improve the
dispersion stability. For instance, recent advances in the art have seen
the advent of coated particles, particles whose surfaces have been
chemically modified, and particles that are covalently bonded to a
dispersant.
While much of the effort has had general application at improving
dispersion stability, some of that effort has not found utility in
particular applications. For example, pigment dispersions used in ink jet
printing applications have very unique and demanding requirements. Ink jet
printing is a non-impact and non-contact printing process in which an
electronic signal produces droplets of ink that are deposited on a wide
variety of substrates such as paper, transparent film, plastics, metals
and fabrics. Typically, the ink is ejected from a printhead containing a
plurality of very small nozzles using thermal or piezoelectric ejection
technology. In ink jet printing, it is critical that the ink components
remain stable, not only in storage but also over repeated firing cycles;
that they not interact with the components used to manufacture the
printhead; that they not clog the nozzle openings; and that they not for a
film on the orifice plate or resistors used in the printhead. In addition,
because such printing is often used in an office environment, such inks
tend to be aqueous based dispersions.
SUMMARY OF THE INVENTION
In the broadest sense, the present invention provides a dispersion of
particles in a liquid vehicle, comprising:
(a) a liquid vehicle selected from the group consisting of water, organic
solvents and combinations thereof;
(b) particles that are at least substantially insoluble in the liquid
vehicle;
(c) a polymer dispersant having at least one segment soluble in the liquid
vehicle and at least one segment insoluble in the liquid vehicle,
(d) wherein said at least one insoluble segment has cross-linking moieties
that are cross-linked to at least one cross-linkable component which is at
least substantially insoluble in the liquid medium and is selected from
the group consisting of itself, a polyfunctional monomer, a polyfunctional
oligomer, and a polyfunctional polymer to form an encapsulation network
which entraps the particles.
In further embodiments, the dispersion may also contain a catalyst to
facilitate the cross-linking reaction. The particles may be organic or
inorganic and the particles may or may not be covalently bonded to the
dispersant.
DETAILED DESCRIPTION OF THE EMBODIMENTS
The dispersions of this invention essentially comprise a liquid vehicle,
particles and a dispersant polymer that has been cross-linked to entrap
the particles. In further embodiments the dispersion may contain a
cross-linking component and catalysts. Depending on the ultimate use of
the dispersions, various additives and adjuvants may be used in the
dispersion as is common in the particular application of interest.
Liquid Vehicle
The liquid vehicle, while an essential component of the invention, may be
aqueous or non-aqueous and may contain water, organic solvents or
combinations thereof. The particular type and amount of liquid will be
readily determined by the particular end use of the dispersions. For
example, the paint industry utilizes both solvent based and aqueous based
paints, stains and coatings. In ink jet ink applications, the vehicle
typically comprises a mixture of water and at least one water soluble
organic solvent, most commonly a pyrrolidone or a polyhydric alcohol, or
both. Generally speaking, there is a strong preference (for environmental,
cost and health and safety reasons) to utilize aqueous based dispersions
wherever possible. Accordingly, an aqueous based liquid vehicle (i.e., a
liquid vehicle comprising at least 50% by weight of water) is a preferred
embodiment of the present invention.
Particles
Although particles are required for the invention, the type and composition
of the particles is not particularly critical and will largely depend upon
the ultimate end use application of the dispersion. By definition, the
particles are at least substantially insoluble in the liquid vehicle. If
they were soluble, the resulting mixture would be a solution rather than a
dispersion. Apart from that general limitation, the particles may be
organic, inorganic or mixtures thereof. Examples of suitable particles
include pigments, insoluble dyes, metallic particles, biologically active
compounds, pharmaceutically active compounds, polymer particles, hollow
glass spheres, etc.
The particle size can have an effect on dispersion stability. In general,
smaller particles tend to create more stable dispersions in that Brownian
motion helps to prevent the particles from flocculating or settling. Small
particle size pigments also produce maximum color strength and there fore
may be desirable in applications using pigment dispersions. The particle
size will vary substantially depending upon the desired end use for the
dispersion. For ink jet ink applications, for example, a useful particle
size will be in the range of 0.005 to 15 microns. For paints, the particle
size may be as high as 75 to 100 microns and in other coatings the
particles may be up to several hundred microns. One of ordinary skill in
the art can readily determine the appropriate particle size for the
desired application.
Fine particles of metal (such as copper, iron, steel, aluminum and alloys)
or metal oxides (e.g., silica, alumina, titania) may be used to practice
the invention. For example, metal and metal oxides are suitable for the
preparation of magnetic and/or optical recording media. In addition, some
coating applications might utilize metallic flakes in combination with
pigments to provide a "pearl-like" finish.
The amount of particles used in the dispersion is not critical to the
invention and can be as desired for the end use application. For instance,
paints, inks and cosmetics may require significantly greater particle
concentrations on a weight basis compared to dispersions of highly
reactive pharmaceutical or agricultural compounds. In a preferred
embodiment, the particles comprise pigments.
Polymer Dispersant:
The function of the polymeric dispersant is to disperse the insoluble
particles in the liquid vehicle. Structured polymers are particularly
preferred. The term "structured polymer" means any polymer that does not
have a random structure. Stated differently, the term "structured polymer"
means that the polymer has identifiable and defined segments or areas
based on the type, identity and/or behavior of the monomers contained
within the segment or area. Typically, but not always, those segments are
characterized as being hydrophobic or hydrophilic.
Examples of structured polymers include block polymers, graft polymers,
tapered polymers and branch polymers. Particularly preferred structured
polymeric dispersants for use in the present invention are block and graft
copolymers. Structured polymers are particularly preferred because it is
easier to produce segments having the desired functionality in such
polymers versus random polymers. Graft polymers having an insoluble
backbone and soluble arms are particularly preferred. Such polymers can be
prepared by techniques well known in the art. For example, block polymers
can be made using the well known Group Transfer Polymerization technique
and graft polymers may be prepared using chain transfer agents. Specific
conditions for preparing particularly preferred polymers are set forth in
the examples.
Regardless of the structure of the polymer dispersant, it must contain one
or more segments that are soluble in the liquid vehicle and one or more
segments that are insoluble in the vehicle. As such, the polymer has an
area or segment that has an affinity for the liquid vehicle and an area or
segment that has an aversion for the liquid vehicle. When the polymer is
placed into the liquid, it will naturally tend to orient itself such that
the segment(s) with aversion to the liquid is/are clustered together to
form a liquid adverse "core" and the segment(s) with affinity for the
vehicle are aligned away from the core. The particles, which are insoluble
and thus also have an aversion for the liquid, tend to migrate into the
"core" formed by the polymer alignment.
Generally speaking, the insoluble particle is relatively content to stay
isolated in this liquid free "core". Under certain conditions, however,
such as changes in temperature, changes in composition of the liquid
vehicle, etc. the particles tend to move out of the core where they can
flocculate and precipitate. The present invention addresses this problem
by cross-linking the insoluble polymer segment to form a network or matrix
around the particle which is extremely resistant to changes in liquid
vehicle composition, temperature and other factors known to destabilize
dispersions. The particle is entrapped in a network formed by the
insoluble polymer segment and the cross-linking bonds 24. The
cross-linking bonds are very stable and effectively prevent the particle
from leaving the "core" formed by the polymer. The soluble segment of the
polymer remains aligned into the liquid vehicle and away from the liquid
adverse "core". It is not necessary that the particle be covalently bonded
to the polymer dispersant to obtain the improved dispersion stability.
However, although not illustrated, it is understood that the dispersions
of the present invention do not preclude situations where the particle, in
addition to being entrapped in the cross-linked matrix, would also be
covalently bonded to the polymer.
The monomer composition of the soluble segment and the insoluble segment of
the dispersant will, of course, depend upon the liquid vehicle selected
for the dispersion. If an aqueous vehicle is selected, the soluble segment
will contain hydrophilic monomers and the insoluble segment will contain
hydrophobic monomers. If a non-aqueous vehicle (that is, one containing
primarily organic solvents) is selected, the opposite would be true.
Therefore, for ease of reference, the useful monomers can be classified
generally as hydrophobic or hydrophilic and will be so categorized herein.
It is also possible to introduce solubility by making a salt of the
monomers used in the soluble segment, particularly for aqueous
dispersions, as is known in the art. Whatever the precise composition of
the soluble segment may be, it is important that this segment be such that
the entire polymer dispersant (or a salt thereof) is soluble in the liquid
vehicle.
Hydrophobic and hydrophilic monomers are well known to those skilled in the
art. Particularly useful hydrophobic monomers (which are soluble in a
non-aqueous vehicle) include:
1) alkyl, aryl, and alkyl aryl acrylates or methacrylates having 1-12
carbon atoms in the alkyl group and/or 6-12 carbons in the aryl group such
as methyl, ethyl, butyl, propyl, isobutyl, hexyl 2-ethyl hexyl, nonyl,
lauryl, isobornyl, benzyl acrylates and methacrylates and the like;
2) polymerizable vinyl aromatic monomers such as styrene, alpha methyl
styrene, vinyl toluene and the like; and
3) aliphatic hydrocarbon monomers such as isoprene and butadiene.
Particularly useful hydrophilic monomers (i.e., those which can impart
water-solubility) include: (1) acid monomers such as acrylic acid,
methacrylic acid, acrylamidomethylpropane sulfonic acid, itaconic acid,
maleic acid and styrene sulfonic acid; (2) amine-containing monomers such
as 2-dimethylaminoethyl methacrylate, 2-dimethylaminoethyl acrylate,
2-diethylaminoethyl methacrylate, and 2-diethylaminoethyl acrylate; and
(3) monomers having oligoether moieties of the general formula:
CH.sub.2 =CRC (O) O (CH.sub.2 CH.sub.2 ).sub.n R.sub.1
wherein R=H or methyl; R.sub.1 =alkyl of 1 to 4 carbon atoms, aryl of 6 to
12 carbon atoms, or alkyl-aryl, and n=1 to 20, examples of which include
ethoxyethyl methacrylate, butoxyethyl methacrylate, ethoxytriethylene
methacrylate, methoxy-polyethylene glycol methacrylate, and
2-ethoxytriethylene glycol methacrylate.
It may be necessary to neutralize the monomers to make them soluble.
Suitable reagents to neutralize the acid monomers include mono-, di-,
tri-methylamine, morpholine, n-methyl morpholine; alcohol amines such as
dimethylethanolamine (DMEA), methyldiethanolamine, mono-, di-, and
tri-ethanolamine; pyridine; ammonium hydroxide; tetra-alkylammonium salts
such as tetramethylammonium hydroxide, tetraethyl-ammonium hydroxide;
alkali metals hydroxides such as lithium, sodium and potassium hydroxide,
aminopropanol, etc. The amine monomers may be neutralized with inorganic
and organic acid such as acetic acid, formic acid, oxalic acid, dimethylol
propionic acid, hydrochloric acid, p-toluene sulfonic acid, benzene
sulfonic acid, nitric acid, citric acid, and the like; halogens such as
chloride, fluoride, and bromide, and inorganic acids, such as sulfuric
acid, nitric acid, phosphoric acid and the like. It is also possible to
convert the amino group into a tetra-alkyl ammonium salt. Alternatively,
the amine functionalities can be rendered water-soluble by quaternization
with reagents such as benzyl chloride, dimethylsulfate, methyl chloride,
etc.
Depending on the number, n, of oxyethylene units in the monomers containing
oligoether moieties, the polymer can be slightly or completely water
soluble. The solubility of the polymer increases as the number of
oxyethylene units increases. The monomers having oligoether moieties can
be advantageously used to adjust the physical properties, such as Tg, of
the polymer dispersant.
In accordance with the invention, the insoluble segment(s) of the polymer
have cross-linkable functional moieties. The insoluble segment(s) of the
dispersant is thus capable of cross-linking to itself or to an additional
cross-linking compound (e.g., monomer, oligomer, or polymer) that has
suitable cross-linking functionality. Table 1 identifies suitable
functional groups that may be incorporated into the insoluble segment of
the dispersant and the companion cross-linking group that may be present
in the cross-linking compound.
TABLE 1
FUNCTIONAL
GROUP CROSS-LINKING GROUP
epoxy amine, anhydride, acid, phenolic,
hydroxyl, N-methylol, aldehyde, acetoacetoxy
hydroxyl isocyanate, epoxide, N-methylol, anhydride,
ester
anhydride epoxide, amine, hydroxyl
acid epoxide, N-methylol, isocyanate
cyclic carbonate amine
activated allyl amine, radical initiator
amine aldehyde, epoxide, anhydride, isocyanate, ester,
acetoacetoxy, activated allyl
silane, silicate, silanol, hydroxyl, water, acid, isocyanate, silane,
silicate
silicone
imine aldehyde, epoxide, anhydride, isocyanate, ester,
acetoacetoxy, activated allyl
Particularly preferred cross-linking combinations are the epoxy moieties
with amines, hydroxyl moieties with isocyanates and silane moieties with
themselves. As noted above, the functional group and the cross-linking
group can be incorporated into the insoluble segment(s) of the polymer
dispersant by selection of appropriate monomers or, preferably, a separate
cross-linking compound having the appropriate group is added to the
dispersion. Useful cross-linking compounds are those which are insoluble
in the liquid vehicle and which do not have significant reaction with the
major component of the liquid vehicle. For aqueous dispersions useful
cross-linking compounds include diacrylate, diisocyanate,
m-tetramethylxylene diisocyanate ("m-TMXDI"), hexamethylene diisocyanate
trimer ("HMDI") and isophorone diisocyanate trimer ("IPDI"). m-TMXDI is
particularly preferred.
The dispersions of the present invention are made in essentially the same
manner as dispersions in the prior art. The particles are premixed with
the selected dispersant and then charged to a suitable dispersion
apparatus (e.g., a media mill, attritor, 2-roll mill, etc.) and thoroughly
mixed. The cross-linking reaction then takes place and the cross-linking
compound (if used) is added to the mixture. To facilitate the
cross-linking reaction, it may be desirable to add a catalysts and/or to
elevate the temperature of the mixture. Useful catalysts can be those that
are either soluble or insoluble in the liquid and are selected depending
upon the cross-linking groups. For isocyanate--hydroxy type cross-linking
reactions, suitable catalysts include (for aqueous systems) dibutyltin
dilaurate ("DBTDL"), tributyl amine ("TBA"), trioctyl amine, tridodecyl
amine and dimethyldodecyl amine. DBTDL and TBA are particularly preferred
for aqueous dispersions. For non-aqueous systems,
2,2,2-diaminobicyclooctane ("DABCO") may be used as the catalyst.
Other Ingredients
The dispersions of this invention may also contain other ingredients or
additives depending on the particular end use. For example, surfactants
are commonly used in coatings such as paint or inks to alter surface
tension as well as maximize penetration into the substrate (for ink
applications in particular). Normally, care must be taken in selecting the
surfactant, however, because the surfactant can compete for the particles
(i.e., pigments) and thus may destabilize the dispersion. The entrapment
of the particles in accordance with the present invention, however, should
permit greater latitude in selecting surfactants.
Biocides are also commonly used in dispersions to inhibit growth of
microorganisms. Sequestering agents, such as EDTA, are also commonly used
to eliminate deleterious effects of heavy metal impurities. Other common
additives include humectants, viscosity modifiers, binders, coating aides,
thickeners and the like, depending on the desired end use of the
dispersion.
EXAMPLES
The invention will now be further illustrated by, but not limited to, the
following examples, in which parts and percentages are by weight unless
otherwise noted.
Example 1
This Example describes the synthesis, dispersion and encapsulation of a
graft copolymer with anionic hydrophilic arms, and a hydrophobic backbone.
A macromonomer was prepared by charging the following components to a 2
liter flask equipped with a thermocouple, stirrer, dropping funnels,
reflux condenser, and the means for bubbling nitrogen through the
reaction.
Parts
Portion 1
Methyl methacrylate monomer 140.92
Methacrylic acid monomer 61.60
Isopropanol 259.80
Portion 2
Methylethyl ketone 8.04
Isopropanol 18.76
Isopropyl-bis(borondifluoro- 0.02
dimethylglyoximato) cobaltate (III) ("DMG Co(III)")
catalyst
VAZO .RTM.-52 Initiator 0.20
Portion 3
Isopropanol 15.60
Portion 4
DMG Co (III) Catalyst 0.04
VAZO .RTM.-52 Initiator 2.20
Methylethyl ketone 24.06
Isopropanol 56.14
Portion 5
Methyl methacrylate monomer 90.10
Methacrylic acid monomer 92.40
Portion 1 was heated to its reflux temperature in about 15 minutes. Portion
2 was thoroughly mixed and added all at once and the composition was held
at its reflux temperature for 5 minutes. The vessel which contained
Portion 2 was rinsed with Portion 3, which was then added to the reaction
vessel. Portions 4 and 5 were added simultaneously to the reaction vessel
while the vessel maintained its reflux temperature. For Portion 4, the
first 54.8% was added over 90 minutes, and the remaining 45.2% was added
over 240 minutes. For Portion 5, the first 67% was added over 120 minutes
and the remaining 33% was added over an additional 120 minutes. After
Portions 4 and 5 have been added to the vessel, the reaction is held at
reflux for an additional 45 minutes and then cooled to room temperature.
The resulting macromonomer solution has a solids content of approximately
50%, and contained 60% methyl methacrylate and 40% methacrylic acid. This
polymer has an approximate weight average molecular weight of 3100, and
number average molecular weight of 2000.
A graft copolymer was then prepared from the macromonomer by charging the
following components to a 10 liter flask equipped as above:
Parts
Portion 1
Macromonomer (prepared above) 3079.00
2-Ethylhexyl acrylate monomer 206.11
Hydroxyethyl acrylate monomer 227.81
Isopropanol 600.00
Portion 2
tertbutylperpivalate (Lupersol .RTM.-11) 25.95
Isopropanol 75.51
Portion 3
2-Ethylhexyl acrylate 1511.49
Hydroxyethyl acrylate 1679.59
Portion 4
VAZO .RTM.-52 initiator 25.95
Methylethyl ketone 24.51
Isopropanol 235.05
Portion 5
VAZO .RTM.-52 Initiator 51.90
Methylethyl ketone 62.46
Isopropanol 149.59
Portion 1 was heated to reflux temperature over a period of approximately
20 minutes. Portion 2 was mixed and charged to the reactor in two equal
portions. After the first was added, the reaction was held at reflux for
10 minutes before the second half was added. After the second half of
Portion 2 was added, the reaction was held at reflux for 10 minutes.
Portions 3 and 4 were added simultaneously to the reaction vessel while
maintaining a reflux in the reaction vessel. Portion 3 was added over 180
minutes, and Portion 4 was added over 240 minutes. After the additions of
Portions 3 and 4 were completed, Portion 5 was added to the reaction
vessel over 15 minutes, maintaining the reflux temperature. After the
addition of Portion 5 was completed, the reaction mixture was maintained
at reflux for 120 minutes and then cooled to room temperature.
The resulting graft copolymer solution had a solids content of
approximately 63% by weight and had the following overall approximate
composition: 33.25% 2-ethylhexyl acrylate; 36.75% hydroxyethyl acrylate;
18% methyl methacrylate and 12% methacrylic acid. This material had a
weight average molecular weight of approximately 21,000 and a number
average molecular weight of approximately 7800.
A waterborne pigment dispersion was prepared by charging the following
constituents into an 01-Attritor media mill:
Parts
Portion 1
Graft copolymer prepared above 54.44
2-amino-2-methyl-1-propanol ("AMP") 5.31
Deionized water 237.75
Portion 2
Quinacridone magenta pigment 52.50
Zirconia media (0.8-1.0 mm) 850.00
The graft copolymer is mixed with the neutralizing agent (AMP) and
deionized water to form Portion 1. The material from Portion 1 was mixed
with the materials in Portion 2 and the constituents were ground for 16
hours at 500 rpm in an 01-Attritor at 100.degree. F. A uniform,
transparent, waterborne pigment dispersion was formed that was stable and
deflocculated and had a pH range of 7.5-8.5. This dispersion contains 15%
pigment and 10% polymer.
This material was used in an encapsulation reaction that involves a
crosslinking reaction between hydroxyl groups in the backbone and a
hydrophobic diisocyanate/catalyst system.
Ingredient Amount
Waterborne dispersion prepared above (10% polymer, 15% 20.00 g
pigment)
m-Tetramethylxylene diioscyanate crosslinker 0.34 g
(isocyanate:OH = 0.4:1.0)
Dibutyltin dilaurate (100% solution) 1 drop
The above ingredients were mixed together and heated at 40-50.degree. C.,
with efficient stirring, for a period of 6 hours. After this time period,
the mixture is cooled to room temperature and tested for flocculation
stability. Samples of both the encapsulated, and unencapsulated pigment
dispersions were tested for flocculation stability by adding 0.5 g of the
sample to different concentrations of an incompatible vehicle, such as
butyl cellosolve in water, which would flocculate the unencapsulated
dispersion. The encapsulated samples were stable in much more aggressive
vehicle formulations (often in 100% butyl cellosolve).
Example 2
This Example describes the synthesis, dispersion and encapsulation of a
graft co-polymer with nonionic hydrophilic arms, and a hydrophobic
backbone.
The following components were charged into a 1 liter flask equipped as
above to form a graft copolymer solution:
Parts
Portion 1
Bisomer S20W (a polyethyleneglycol methacrylate, 37.93
49% solids in water, Mn = 2000, available from
International Specialty Chemicals)
Hydroxyethyl acrylate 6.56
n-Butyl acrylate 5.93
Isopropanol 191.94
Portion 2
n-Butyl acrylate 43.52
Hydroxyethyl acrylate 48.10
Bisomer S20W 278.17
Portion 3
VAZO .RTM.-52 Initiator 1.31
Methylethyl ketone 1.24
Isopropanol 21.97
Portion 4
VAZO .RTM.-52 initiator 2.62
Methylethyl ketone 3.15
Isopropanol 7.56
Portion 1 was heated to reflux temperature over a period of approximately
20 minutes. Portions 2 and 3 were added simultaneously to the reaction
vessel while maintaining a reflux in the reaction vessel. Portion 2 was
added over 180 minutes, and Portion 3 was added over 240 minutes. After
the additions of Portions 2 and 3 were completed, Portion 4 was added to
the reaction vessel over 15 minutes, maintaining the reflux temperature.
After the addition of Portion 4 was completed, the reaction mixture was
maintained at reflux for 120 minutes and then cooled to room temperature.
The resulting graft copolymer solution had a solids content of
approximately 40% by weight and had the following overall approximate
composition: 19% n-butyl acrylate; 21% hydroxyethyl acrylate; and 60%
Bisomer S20W. This material had a weight average molecular weight of
approximately 12300 and a number average molecular weight of approximately
5700.
A waterborne pigment dispersion was prepared by charging the following
constituents into an 01-Attritor media mill:
Parts
Portion 1
Graft copolymer prepared above 87.98
Deionized water 209.52
Portion 2
Quinacridone magenta pigment 52.50
Zirconia media (0.8-1.0 mm) 850.00
The graft copolymer is mixed with the deionized water to form Portion 1 (no
neutralizing agent is needed). The material from Portion 1 was mixed with
the materials in Portion 2 and the constituents were ground for 16 hours
at 500 rpm in an 01-Attritor at 100.degree. F. A uniform, transparent,
waterborne pigment dispersion was formed that was stable and deflocculated
and had a pH range of 2-4. This dispersion contains 15% pigment and 10%
polymer.
This material was used in an encapsulation reaction that involves a
crosslinking reaction between hydroxy groups in the backbone and a
hydrophobic dissocyanate/catalyst system.
Ingredient Amount
Waterborne dispersion prepared above (10% polymer, 20.00 g
15% pigment)
m-Tetramethylxylene diisocyanate crosslinker 0.34 g
(isocyanate:OH = 0.4:1.0)
Dibutyltin dilaurate (100% solution) 1 drop
The above constituents mixed together and heated at 40-50.degree. C., with
efficient stirring, for a period of 6 hours. After this time period, the
mixture is cooled to room temperature and tested for flocculation
stability. Samples of both the encapsulated and unencapsulated pigment
dispersions were tested for flocculation stability as in Example 1. The
encapsulated samples were stable in much more aggressive vehicle
formulations compared to the unencapsulated samples.
Example 3
This Examples describes the synthesis, dispersion and encapsulation of a
graft copolymer with cationic hydrophilic arms, and a hydrophobic
backbone.
The following components were charged into a 1 liter flask equipped as
above to form a graft copolymer solution:
Parts
Portion 1
Dimethylaminoethyl methacrylate ("DMABMA") 29.60
macromonomer (50.6% solids; MW = 8000; containing
about 51 DMAEMA units)
Hydroxyethyl acrylate 18.25
2-Ethylhexyl acrylate 16.51
Isopropanol 60.88
Portion 2
Luperisol .RTM.- 11 initiator 2.08
Isopropanol 6.05
Portion 3
2-Ethylhexyl acrylate 121.07
Hydroxyethyl acrylate 134.53
DMAEMA macromonomer 217.03
Portion 4
VAZO .RTM.-52 initiator 2.08
Methylethyl ketone 1.96
Isopropanol 18.83
Portion 5
VAZO .RTM.-52 initiator 4.16
Methylethyl ketone 5.00
Isopropanol 11.98
Portion 1 was heated to reflux temperature over a period of approximately
20 minutes. Portion 2 was added to Portion 1 in two equal portions 10
minutes apart. After the second half of Portion 2 has been added, the
reaction is held at reflux for 10 minutes. Portions 3 and 4 were added
simultaneously to the reaction vessel while maintaining a reflux. Portion
3 was added over 180 minutes, and Portion 4 was added over 240 minutes.
After the additions of Portions 3 and 4 were completed, Portion 5 was
added to the reaction vessel over 15 minutes, maintaining the reflux
temperature. After the addition of Portion 5 was completed, the reaction
mixture was maintained at reflux for 120 minutes and then cooled to room
temperature.
The resulting graft copolymer solution had a solids content of
approximately 65% by weight and had the following overall approximate
composition: 33% 2-ethylhexyl acrylate; 37% hydroxyethyl acrylate; and 30%
DMAEMA macromonomer. This material had a weight average molecular weight
of approximately 7337 and a number average molecular weight of
approximately 3252.
A waterborne pigment dispersion was prepared by charging the following
constituents into an 01-Attritor media mill:
Parts
Portion 1
Graft copolymer prepared above 54.09
0.1N HCl water solution 243.40
Portion 2
Quinacridone magenta pigment 52.50
Zirconia media (0.8-1.0 mm) 850.00
The graft copolymer is neutralized with the 0.1N HC 1 to form Portion 1.
The material from Portion 1 was mixed with the materials in Portion 2 and
the constituents were ground for 16 hours at 500 rpm in an 01-Attritor at
100.degree. F. A uniform, transparent, waterborne pigment dispersion was
formed that was stable and deflocculated and had a pH range of 2-4. This
dispersion contains 15% pigment and 10% polymer.
This material was used in an encapsulation process involving a crosslinking
reaction between hydroxyl groups in the backbone and a hydrophobic
diisocyanate/catalyst system.
Ingredient Amount
Waterborne dispersion prepared above (10% polymer, 20.00 g
15% pigment)
m-Tetramethylxylene diisocyanate crosslinker 0.28 g
(isocyanate:OH = 0.4:1.0)
Dibutyltin dilaurate (100% solution) 1 drop
The above constituents mixed together and heated at 40-50.degree. C., with
efficient stirring, for a period of 6 hours. After this time period, the
mixture is cooled to room temperature and tested for flocculation
stability as in Example 1. The encapsulated samples were more stable than
the non-encapsulated samples.
Example 4
This Example describes the synthesis, dispersion and encapsulation of a
block copolymer with an anionic hydrophilic block, and a hydrophobic
block.
The following components were charged into a 1 liter flask equipped as
above to form a graft copolymer solution:
Parts
Portion 1
MMA/MAA macromonomer (from Example 1) 227.09
Isopropanol 60.00
Portion 2
Luperisol .RTM.-11 initiator 0.24
Portion 3
2-Ethylhexyl methacrylate 126.68
Hydroxyethyl methacrylate 140.01
Portion 4
VAZO .RTM.-52 Initiator 3.08
Isopropanol 74.50
Portion 1 was placed in the reactor and heated to reflux temperature over a
period of approximately 20 minutes. Portion 2 was added to Portion 1 as a
single shot and the reaction was held for 5 minutes. Portions 3 and 4 were
each mixed thoroughly and added simultaneously to the reaction vessel
while maintaining a reflux in the reaction vessel. Portion 3 was added
over 240 minutes, and Portion 4 was added over 270 minutes. After the
additions of Portions 3 and 4 were completed, the reaction mixture was
maintained at reflux for at least 30 minutes and then cooled to room
temperature.
The resulting block copolymer solution had a solids content of
approximately 60% by weight and had the following overall approximate
composition: 33% 2-ethylhexyl methacrylate; 36% hydroxyethyl methacrylate;
18% methyl methacrylate and 12% methacrylic acid.
A waterborne pigment dispersion was prepared by charging the following
constituents into an 01-Attritor media mill:
Parts
Portion 1
Graft copolymer prepared above 58.54
AMP 7.15
Water 231.81
Portion 2
Quinacridone magenta pigment 52.50
Zirconia media (0.8-1.0 mm) 850.00
The graft copolymer is neutralized with AMP to form Portion 1. The material
from Portion 1 was mixed with the materials in Portion 2 and the
constituents were ground for 16 hours at 500 rpm in an 01-Attritor at
100.degree. F. A uniform, transparent, waterborne pigment dispersion was
formed that was stable and deflocculated and had a pH range of 2-4. This
dispersion contains 15% pigment and 10% polymer.
This material was then used in an encapsulation reaction involving a
crosslinking reaction between hydroxyl groups in the hydrophobic block and
a hydrophobic diisocyanate/catalyst system.
Ingredient Amount
Waterborne dispersion prepared above (10% polymer, 20.00 g
15% pigment)
m-Tetramethylxylene diisocyanate crosslinker 0.7 g
(isocyanate:OH = 1.0:1.0)
Dibutyltin dilaurate (100% solution) 1 drop
The above constituents mixed together and heated at 40-50.degree. C., with
efficient stirring, for a period of 6 hours. After this time period, the
mixture is cooled to room temperature and tested for flocculation
stability as in Example 1, with the same results.
Example 5
This Example describes the synthesis, dispersion and encapsulation of a
random, linear copolymer containing the same portion reactive functional
groups and monomers seen in Examples 1 and 4.
The following components were charged into a 1 liter flask equipped as
above to form a graft copolymer solution:
Parts
Portion 1
Methylethyl ketone 200.00
2-Ethylhexyl methacrylate 31.73
Hydroxyethyl methacrylate 36.40
Methyl methacrylate 20.00
Methacrylic acid 12.04
Portion 2
Methylethyl ketone 35.00
VAZO .RTM.-67 5.00
Portion 3
2-Ethylhexyl methacrylate 126.90
Hydroxyethyl methacrylate 145.60
Methyl methacrylate 80.00
Methacrylic acid 48.16
Portion 4
Methylethyl ketone VAZO .RTM.-52 65.00
VAZO .RTM.-67 10.00
Portion 1 was placed in the reactor and heated to reflux temperature over a
period of approximately 20 minutes. Portion 2 was added to Portion 1 over
one minute and the reaction was held for 5 minutes. Portions 3 and 4 were
added simultaneously to the reaction vessel while maintaining a reflux in
the reaction vessel. Portion 3 was added over 240 minutes, and Portion 4
was added over 300 minutes. After the additions of Portions 3 and 4 were
completed, the reaction mixture was maintained at reflux for at least 30
minutes and then cooled to room temperature.
The resulting linear, random copolymer solution had a solids content of
approximately 58% by weight and had the following overall approximate
composition: 33% 2-ethylhexyl methacrylate; 36% hydroxyethyl methacrylate;
18% methyl methacrylate and 12% methacrylic acid.
A waterborne pigment dispersion was prepared by charging the following
constituents into an 01-Attritor media mill:
Parts
Portion 1
Copolymer prepared above 59.96
AMP 6.98
Water 230.56
Portion 2
Quinacridone magenta pigment 52.50
Zirconia media (0.8-1.0 mm) 850.00
The copolymer is neutralized with the AMP to form Portion 1. The material
from Portion 1 was mixed with the materials in Portion 2 and the
constituents were ground for 16 hours at 500 rpm in an 01-Attritor at
100.degree. F. A uniform, transparent, waterborne pigment dispersion was
formed that was stable and deflocculated and had a pH range of 2-4. This
dispersion contains 15% pigment and 10% polymer.
This material was used in the following encapsulation reaction.
Ingredient Amount
Waterborne dispersion prepared above 20.00 g
(10% polymer, 15% pigment)
m-Tetramethylxylene diisocyanate 0.7 g
crosslinker (isocyanate:OH = 1.0:1.0)
Dibutyltin dilaurate (100% solution) 1 drop
The above constituents mixed together and heated at 40-50.degree. C., with
efficient stirring, for a period of 6 hours. After this time period, the
mixture is cooled to room temperature and tested for flocculation
stability as in Example 1. The encapsulated samples were more stable.
Example 6
This Example describes the synthesis, dispersion and encapsulation of a
graft copolymer with nonionic, hydrophilic arms, and a hydrophobic
backbone containing a glycidyl methacrylate functional group. This is an
example of an encapsulation reaction using a different type of
crosslinker. Nonionic, hydrophilic arms are necessary because the glycidyl
methacrylate group would react with the acid groups found in the
hydrophilic arms of Example 1.
The following components were charged into a 2 liter flask equipped as
above to form a graft copolymer solution:
Parts
Portion 1
Bisomer S20W 60.35
Glycidyl methacrylate 12.15
n-Butyl acrylate 18.22
Isopropanol 440.26
Portion 2
n-Butyl acrylate 133.63
Glycidyl methacrylate 89.09
Bisomer S20W 442.54
Portion 3
VAZO .RTM.-52 Initiator 2.54
Methylethyl ketone 2.40
Isopropanol 23.00
Portion 4
VAZO .RTM.-52 Initiator 5.08
Methylethyl ketone 6.11
Isopropanol 14.64
Portion 1 was heated to reflux temperature over a period of approximately
20 minutes. Portions 2 and 3 were added simultaneously to the reaction
vessel while maintaining a reflux in the reaction vessel. Portion 2 was
added over 180 minutes, and Portion 3 was added over 240 minutes. After
the additions of Portions 2 and 3 were completed, Portion 4 was thoroughly
mixed and added to the reaction vessel over 15 minutes, maintaining the
reflux temperature. After the addition of Portion 4 was completed, the
reaction mixture was maintained at reflux for 120 minutes and then cooled
to room temperature.
The resulting graft copolymer solution had a solids content of
approximately 41% by weight and had the following overall approximate
composition: 30% n-butyl acrylate; 20% gylcidyl methacrylate; and 50%
bisomer S20W. This material had a weight average molecular weight of about
24000 and a number average molecular weight of approximately 9000.
A waterborne pigment dispersion was prepared by charging the following
constituents into an 01-Attritor media mill.
Parts
Portion 1
Graft copolymer prepared above 88.72
Deionized water 208.78
Portion 2
Quinacrodone magenta pigment 52.50
Zirconia media (0.8-1.0 mm) 850.00
The graft copolymer is mixed with deionized water to form Portion 1 (no
neutralizing agent is needed). The material from Portion 1 was mixed with
the materials in Portion 2 and the constituents were ground for 16 hours
at 500 rpm in an 01-Attritor at 100.degree. F. A uniform, transparent,
waterborne pigment dispersion was formed that was stable and deflocculated
and had a pH range of 2-4. This dispersion contains 15% pigment and 10%
polymer.
This material was then encapsulated by a crosslinking reaction between
epoxide groups in the backbone and a hydrophobic diamine/catalyst system.
Ingredient Amount
Waterborne dispersion prepared above (10% polymer, 20.00 g
15% pigment)
Norbornenediamine crosslinker (amine:glycidyl 0.17 g
methacrylate = 1.0:1.0)
Tributyl amine 1 drop
The above constituents mixed together and heated at 40-50.degree. C., with
efficient stirring, for a period of 6 hours. After this time period, the
mixture is cooled to room temperature and tested for flocculation
stability as in previous examples. The encapsulated samples were tested as
in Example 1 and were more stable than the non-encapsulated samples.
Example 7
Two inks were prepared from unencapsulated and encapsulated dispersions and
a third ink was prepared from a conventional dispersion to test the
stability to thermal cycling achieved with the encapsulated dispersion as
well as printability in an ink jet printing device.
Dispersion #1 contains a quinacridone magenta pigment and a dispersant of
the type prepared in Example 1, the dispersion was prepared using a two
roll mill process and was let down into water to 15% by weight pigment and
2.5 parts pigment to 1 part dispersant. Dispersion #2 is dispersion #1
encapsulated using the process described in Example 1. Dispersion #3 uses
a conventional methacrylic dispersant and a quniacridone magenta pigment
and was prepared using a two roll mill process and was let down into water
to 15% pigment and 1.5 parts pigment to 1 part dispersant. Vehicle #1
contains 100 grams of an ethoxylated glycerol, 100 grams of 1,2 hexane
diol, 100 grams of diethylene glycol, 27 grams of sodium dioctyl
sulfosuccinate and the balance water to a total weight of 1000 grams.
Ink #1 was prepared by adding 11 grams of dispersion #1, 25 grams of
vehicle #1 and the balance water to a total of 50 grams. Ink #2 was
prepared by adding 11 grams of dispersion #2, 25 grams of vehicle #1 and
the balance water to a total of 50 grams. Ink #3 was prepared by adding 11
grams of dispersion #3, 25 grams of vehicle #1 and the balance water to a
total of 50 grams.
The inks were then tested in an ink jet printer and all printed well. The
inks were also subjected to four freeze--thaw cycles from -20.degree. C.
to 60.degree. C. and the change in particle size was observed. While all
inks showed an increase in average particle size, the encapsulated sample
(Ink #2) increased in size by about 25% versus the 187% increase for Ink
#1 and 132% increase for Ink #3. This data indicates that Ink#2 is more
stable to thermal cycling.
Example 8
A tint suitable for use in manufacture of paint was prepared to demonstrate
the utility of the present invention in such a process. Following the
process of Example 1, a dispersion containing copper phthalocyanine blue
pigment was prepared, ground and encapsulated. The resulting dispersion
was then adjusted to a pH of 9 and the appearance of the dispersion
drawdown (i.e., color and haze), and the percentage of solids, were
compared to a standard sample.
Following the standardization of the dispersion, it was mixed with a base
coat latex, water, a thickener and a biocide. The final solution pH,
tinting strength and viscosity were monitored and additional water and/or
thickener added to maintain standard viscosity and tint strength.
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